﻿using System.Security.Cryptography;

namespace System;

/// <summary>
/// 国密 SM4 加解密
/// </summary>
public class SM4 : IDisposable
{
    public SM4CipherMode Mode { get; set; } = SM4CipherMode.CBC;

    public bool Padding { get; set; } = true;

    private long[] SK = new long[32];

    private const int BlockSize = 128;
    private const int KeySize = 128;
    private const int BitsPerByte = 8;

    private byte[]? IVValue;
    private byte[]? KeyValue;

    public byte[] IV
    {
        get
        {
            if (IVValue == null)
                GenerateIV();
            return IVValue.CloneByteArray()!;
        }

        set
        {
            ArgumentNullException.ThrowIfNull(value);
            if (value.Length != BlockSize / 8)
                throw new CryptographicException("Specified initialization vector (IV) does not match the block size for this algorithm.");

            IVValue = value.CloneByteArray();
        }
    }

    public virtual byte[] Key
    {
        get
        {
            if (KeyValue == null)
                GenerateKey();
            return KeyValue.CloneByteArray()!;
        }

        set
        {
            ArgumentNullException.ThrowIfNull(value);
            if (value.Length != KeySize / 8)
                throw new CryptographicException("Specified key is not a valid size for this algorithm.");
            KeyValue = value.CloneByteArray();
        }
    }

    /// <summary>
    /// 加密
    /// </summary>
    /// <param name="input"></param>
    /// <returns></returns>
    public byte[] Encrypt(byte[] input)
    {
        SetEncrytKey();

        if (Padding)
            input = EncryptPadding(input);

        if (Mode == SM4CipherMode.ECB)
            return ECBCryptoTransform(input);

        return CBCEncryptTransform(input);
    }

    /// <summary>
    /// 解密
    /// </summary>
    /// <param name="input"></param>
    /// <returns></returns>
    public byte[] Decrypt(byte[] input)
    {
        SetDecrytKey();

        byte[] output;
        if (Mode == SM4CipherMode.ECB)
            output = ECBCryptoTransform(input);
        else
            output = CBCDecryptTransform(input);

        if (Padding)
            output = DecryptPadding(output);

        return output;
    }

    private long GetULong(byte[] b, int i)
    {
        long n = (long)(b[i] & 0xff) << 24 | (long)((b[i + 1] & 0xff) << 16) | (long)((b[i + 2] & 0xff) << 8) | (long)(b[i + 3] & 0xff) & 0xffffffffL;
        return n;
    }

    private void PutULong(long n, byte[] b, int i)
    {
        b[i] = (byte)(int)(0xFF & n >> 24);
        b[i + 1] = (byte)(int)(0xFF & n >> 16);
        b[i + 2] = (byte)(int)(0xFF & n >> 8);
        b[i + 3] = (byte)(int)(0xFF & n);
    }

    private long SHL(long x, int n)
    {
        return (x & 0xFFFFFFFF) << n;
    }

    private long ROTL(long x, int n)
    {
        return SHL(x, n) | x >> (32 - n);
    }

    private void Swap(long[] sk, int i)
    {
        long t = sk[i];
        sk[i] = sk[(31 - i)];
        sk[(31 - i)] = t;
    }

    private byte[] SboxTable = new byte[] {
            0xd6, 0x90, 0xe9, 0xfe, 0xcc, 0xe1, 0x3d, 0xb7,
            0x16, 0xb6, 0x14, 0xc2, 0x28, 0xfb, 0x2c, 0x05,
            0x2b, 0x67, 0x9a, 0x76, 0x2a, 0xbe, 0x04, 0xc3,
            0xaa, 0x44, 0x13, 0x26, 0x49, 0x86, 0x06, 0x99,
            0x9c, 0x42, 0x50, 0xf4, 0x91, 0xef, 0x98, 0x7a,
            0x33, 0x54, 0x0b, 0x43, 0xed, 0xcf, 0xac, 0x62,
            0xe4, 0xb3, 0x1c, 0xa9, 0xc9, 0x08, 0xe8, 0x95,
            0x80, 0xdf, 0x94, 0xfa, 0x75, 0x8f, 0x3f, 0xa6,
            0x47, 0x07, 0xa7, 0xfc, 0xf3, 0x73, 0x17, 0xba,
            0x83, 0x59, 0x3c, 0x19, 0xe6, 0x85, 0x4f, 0xa8,
            0x68, 0x6b, 0x81, 0xb2, 0x71, 0x64, 0xda, 0x8b,
            0xf8, 0xeb, 0x0f, 0x4b, 0x70, 0x56, 0x9d, 0x35,
            0x1e, 0x24, 0x0e, 0x5e, 0x63, 0x58, 0xd1, 0xa2,
            0x25, 0x22, 0x7c, 0x3b, 0x01, 0x21, 0x78, 0x87,
            0xd4, 0x00, 0x46, 0x57, 0x9f, 0xd3, 0x27, 0x52,
            0x4c, 0x36, 0x02, 0xe7, 0xa0, 0xc4, 0xc8, 0x9e,
            0xea, 0xbf, 0x8a, 0xd2, 0x40, 0xc7, 0x38, 0xb5,
            0xa3, 0xf7, 0xf2, 0xce, 0xf9, 0x61, 0x15, 0xa1,
            0xe0, 0xae, 0x5d, 0xa4, 0x9b, 0x34, 0x1a, 0x55,
            0xad, 0x93, 0x32, 0x30, 0xf5, 0x8c, 0xb1, 0xe3,
            0x1d, 0xf6, 0xe2, 0x2e, 0x82, 0x66, 0xca, 0x60,
            0xc0, 0x29, 0x23, 0xab, 0x0d, 0x53, 0x4e, 0x6f,
            0xd5, 0xdb, 0x37, 0x45, 0xde, 0xfd, 0x8e, 0x2f,
            0x03, 0xff, 0x6a, 0x72, 0x6d, 0x6c, 0x5b, 0x51,
            0x8d, 0x1b, 0xaf, 0x92, 0xbb, 0xdd, 0xbc, 0x7f,
            0x11, 0xd9, 0x5c, 0x41, 0x1f, 0x10, 0x5a, 0xd8,
            0x0a, 0xc1, 0x31, 0x88, 0xa5, 0xcd, 0x7b, 0xbd,
            0x2d, 0x74, 0xd0, 0x12, 0xb8, 0xe5, 0xb4, 0xb0,
            0x89, 0x69, 0x97, 0x4a, 0x0c, 0x96, 0x77, 0x7e,
            0x65, 0xb9, 0xf1, 0x09, 0xc5, 0x6e, 0xc6, 0x84,
            0x18, 0xf0, 0x7d, 0xec, 0x3a, 0xdc, 0x4d, 0x20,
            0x79, 0xee, 0x5f, 0x3e, 0xd7, 0xcb, 0x39, 0x48
        };

    private uint[] FK = {
            0xa3b1bac6,
            0x56aa3350,
            0x677d9197,
            0xb27022dc
        };

    private uint[] CK = {
            0x00070e15,0x1c232a31,0x383f464d,0x545b6269,
            0x70777e85,0x8c939aa1,0xa8afb6bd,0xc4cbd2d9,
            0xe0e7eef5,0xfc030a11,0x181f262d,0x343b4249,
            0x50575e65,0x6c737a81,0x888f969d,0xa4abb2b9,
            0xc0c7ced5,0xdce3eaf1,0xf8ff060d,0x141b2229,
            0x30373e45,0x4c535a61,0x686f767d,0x848b9299,
            0xa0a7aeb5,0xbcc3cad1,0xd8dfe6ed,0xf4fb0209,
            0x10171e25,0x2c333a41,0x484f565d,0x646b7279
        };

    private byte SM4Sbox(byte inch)
    {
        int i = inch & 0xFF;
        byte retVal = SboxTable[i];
        return retVal;
    }

    private long SM4Lt(long ka)
    {
        long bb = 0L;
        long c = 0L;
        byte[] a = new byte[4];
        byte[] b = new byte[4];
        PutULong(ka, a, 0);
        b[0] = SM4Sbox(a[0]);
        b[1] = SM4Sbox(a[1]);
        b[2] = SM4Sbox(a[2]);
        b[3] = SM4Sbox(a[3]);
        bb = GetULong(b, 0);
        c = bb ^ ROTL(bb, 2) ^ ROTL(bb, 10) ^ ROTL(bb, 18) ^ ROTL(bb, 24);
        return c;
    }

    private long SM4F(long x0, long x1, long x2, long x3, long rk)
    {
        return x0 ^ SM4Lt(x1 ^ x2 ^ x3 ^ rk);
    }

    private long SM4CalciRK(long ka)
    {
        long bb = 0L;
        long rk = 0L;
        byte[] a = new byte[4];
        byte[] b = new byte[4];
        PutULong(ka, a, 0);
        b[0] = SM4Sbox(a[0]);
        b[1] = SM4Sbox(a[1]);
        b[2] = SM4Sbox(a[2]);
        b[3] = SM4Sbox(a[3]);
        bb = GetULong(b, 0);
        rk = bb ^ ROTL(bb, 13) ^ ROTL(bb, 23);
        return rk;
    }

    private void SetEncrytKey()
    {
        long[] MK = new long[4];
        long[] k = new long[36];
        int i = 0;
        MK[0] = GetULong(Key, 0);
        MK[1] = GetULong(Key, 4);
        MK[2] = GetULong(Key, 8);
        MK[3] = GetULong(Key, 12);
        k[0] = MK[0] ^ (long)FK[0];
        k[1] = MK[1] ^ (long)FK[1];
        k[2] = MK[2] ^ (long)FK[2];
        k[3] = MK[3] ^ (long)FK[3];
        for (; i < 32; i++)
        {
            k[(i + 4)] = (k[i] ^ SM4CalciRK(k[(i + 1)] ^ k[(i + 2)] ^ k[(i + 3)] ^ (long)CK[i]));
            SK[i] = k[(i + 4)];
        }
    }

    private void SetDecrytKey()
    {
        SetEncrytKey();
        for (var i = 0; i < 16; i++)
        {
            Swap(SK, i);
        }
    }

    private void Round(long[] sk, byte[] input, byte[] output)
    {
        int i = 0;
        long[] ulbuf = new long[36];
        ulbuf[0] = GetULong(input, 0);
        ulbuf[1] = GetULong(input, 4);
        ulbuf[2] = GetULong(input, 8);
        ulbuf[3] = GetULong(input, 12);
        while (i < 32)
        {
            ulbuf[(i + 4)] = SM4F(ulbuf[i], ulbuf[(i + 1)], ulbuf[(i + 2)], ulbuf[(i + 3)], sk[i]);
            i++;
        }
        PutULong(ulbuf[35], output, 0);
        PutULong(ulbuf[34], output, 4);
        PutULong(ulbuf[33], output, 8);
        PutULong(ulbuf[32], output, 12);
    }

    private byte[] EncryptPadding(byte[] input)
    {
        int p = 16 - input.Length % 16;
        var ret = new byte[input.Length + p];
        Array.Copy(input, 0, ret, 0, input.Length);
        for (int i = 0; i < p; i++)
        {
            ret[input.Length + i] = (byte)p;
        }
        return ret;
    }

    private byte[] DecryptPadding(byte[] input)
    {
        int p = input[input.Length - 1];
        var ret = new byte[input.Length - p];
        Array.Copy(input, 0, ret, 0, input.Length - p);
        return ret;
    }

    private byte[] ECBCryptoTransform(byte[] plainBytes)
    {
        int length = plainBytes.Length;
        byte[] bins = new byte[length];
        Array.Copy(plainBytes, 0, bins, 0, length);
        byte[] bous = new byte[length];
        for (int i = 0; length > 0; length -= 16, i++)
        {
            byte[] inBytes = new byte[16];
            byte[] outBytes = new byte[16];
            Array.Copy(bins, i * 16, inBytes, 0, length > 16 ? 16 : length);
            Round(SK, inBytes, outBytes);
            Array.Copy(outBytes, 0, bous, i * 16, length > 16 ? 16 : length);
        }
        return bous;
    }

    private byte[] CBCEncryptTransform(byte[] input)
    {
        int i = 0;
        int length = input.Length;
        byte[] bins = new byte[length];
        Array.Copy(input, 0, bins, 0, length);
        var bous = new List<byte>();
        for (int j = 0; length > 0; length -= 16, j++)
        {
            byte[] inBytes = new byte[16];
            byte[] outBytes = new byte[16];
            byte[] out1 = new byte[16];

            Array.Copy(bins, i * 16, inBytes, 0, length > 16 ? 16 : length);
            for (i = 0; i < 16; i++)
            {
                outBytes[i] = ((byte)(inBytes[i] ^ IV[i]));
            }
            Round(SK, outBytes, out1);
            Array.Copy(out1, 0, IV, 0, 16);
            for (int k = 0; k < 16; k++)
            {
                bous.Add(out1[k]);
            }
        }
        return bous.ToArray();
    }

    private byte[] CBCDecryptTransform(byte[] input)
    {
        int i = 0;
        int length = input.Length;
        byte[] bins = new byte[length];
        Array.Copy(input, 0, bins, 0, length);
        var bous = new List<byte>();
        byte[] temp = new byte[16];
        for (int j = 0; length > 0; length -= 16, j++)
        {
            byte[] inBytes = new byte[16];
            byte[] outBytes = new byte[16];
            byte[] out1 = new byte[16];

            Array.Copy(bins, i * 16, inBytes, 0, length > 16 ? 16 : length);
            Array.Copy(inBytes, 0, temp, 0, 16);
            Round(SK, inBytes, outBytes);
            for (i = 0; i < 16; i++)
            {
                out1[i] = ((byte)(outBytes[i] ^ IV[i]));
            }
            Array.Copy(temp, 0, IV, 0, 16);
            for (int k = 0; k < 16; k++)
            {
                bous.Add(out1[k]);
            }
        }
        return bous.ToArray();
    }

    private void GenerateIV()
    {
        IV = RandomNumberGenerator.GetBytes(BlockSize / BitsPerByte);
    }

    private void GenerateKey()
    {
        Key = RandomNumberGenerator.GetBytes(KeySize / BitsPerByte);
    }

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    protected virtual void Dispose(bool disposing)
    {
        if (disposing)
        {
            if (KeyValue != null)
            {
                Array.Clear(KeyValue);
                KeyValue = null;
            }
            if (IVValue != null)
            {
                Array.Clear(IVValue);
                IVValue = null;
            }
        }
    }
}

public enum SM4CipherMode
{
    CBC = 1,
    ECB = 2,
}
